Essentials of Vitamin D for our Health

D for health

By Dr Yeap Swan Sim

VITAMIN D is among the fat-soluble vitamins well known for being essential for skeletal health. Osteoporosis and osteoporotic fractures are the consequences of poor skeletal health.

Vitamin D affects fracture risk in 2 ways: by decreasing falls and increasing bone density.

Low vitamin D levels have been associated with lower bone density in adolescents and adults, plus an increased risk of fracture. This increased risk of fracture may be linked with the truth that vitamin D has direct effects on muscle strength modulated by vitamin D receptors in human muscle tissue. Lack of vitamin D results in muscle weakness and pain, which could then result in a person to fall, and thus increase the chance of fracture.

Studies have shown that supplementation from the older population with 700-1000IU of vitamin D daily can help to eliminate the incidence of falls.

In addition to vitamin D's well-known effects on bone health, its deficiency has additionally been implicated in increasing the risk of coronary heart disease, hypertension, heart failure, autoimmune diseases for example diabetes, and certain cancers.

Vitamin D binds to vitamin D receptors (VDR), which are contained in many cells in your body, not only bone cells. Through this mechanism, adequate levels of vitamin D can lower systolic blood pressure, lower levels of LDL ("bad" cholesterol) and triglycerides, affect how well one's heart muscle contracts, and increase insulin secretion and sensitivity, which can impact general cardiovascular health.

Some, although not all, epidemiological studies (studies that appear to be at patterns of health and illness in the population) have suggested that higher levels of vitamin D intake may lessen the chance of certain cancers for example colon or cancer of the breast. However, overall, the studies have not been uniformly conclusive and also the National Cancer Institute in the usa has told you that it remains "unclear" whether vitamin D is associated with a lower chance of certain cancers.

They conclude by not recommending because of or from the utilization of vitamin D supplements to reduce cancer risk.

This article will review how we get vitamin D within our bodies, and just how expensive is enough.

Vitamin D metabolism

There's two types of vitamin D - vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D3 is manufactured in your skin through the action of ultraviolet B (UVB) light on skin cells. Vitamin D2 is plant derived. Both Vitamin D2 and D3 can be obtained from certain foods in the diet or as supplements.

Normally, only about 20% of our daily vitamin D intake is from the diet, due to the limited selection of food which has vitamin D. Thus sunlight is usually our major source of vitamin D.

Once absorbed, vitamin D is converted within the liver to 25-hydroxy vitamin D [25(OH)D]. This really is further converted in the kidneys to 1,25-dihydroxy vitamin D. This is actually the active form of vitamin D, which is responsible for adjusting calcium absorption within the gut to maintain calcium homeostasis. Adequate levels of calcium within the blood is required for mineralisation of bones, the process through which calcium is deposited onto bones, thus making them strong.

Deficiencies in vitamin D would result in reduced levels of calcium being absorbed with the gut, and resulting in 'abnormal' amounts within the blood. As a result, manufacture of a hormone called parathyroid hormone (PTH) is stimulated. PTH compensates for the reduced calcium absorption from the gut by mobilising calcium from the bones. So as to, the quantity of calcium within the bones could possibly get less and also the bones could possibly get weaker.

Severe vitamin D deficiency leads to a condition called rickets in youngsters, where their bones are weak and are more prone to fracture or deform; in grown-ups, vitamin D deficiency can give rise to a condition called osteomalacia, in which the bones are not mineralised properly, resulting in aching and weakness.

Vitamin D requirements

Just how much vitamin D do you need? Based on the above, we should be planning to have enough vitamin D in our bodies so they won't stimulate more PTH production, that is detrimental to the bones. It is generally accepted that assessment of vitamin D levels within our bodies is reflected by the amounts of 25(OH)D.

There is debate regarding exactly what level is adequate, but a level of 25(OH)D above 30 ng/mL (75 nmol/L) would be generally regarded as being sufficient; levels below 20 ng/mL (50 nmol/L) could be deficient; and levels in-between could be insufficient.

In Malaysia, the average level of 25(OH)D is about the low side. Inside a study completed in postmenopausal women residing in the Klang Valley, Malay women had lower average levels (44.4 nmol/L) in contrast to Chinese women (68.8 nmol/L) of 25(OH)D. In part, this may be due to cultural reasons as skin included in clothing won't be able to fabricate vitamin D from sunlight. However, observe that these levels are still in the insufficient range.

Just how much vitamin D do we need daily? The Ministry recommended in 2005 that youngsters and adults as much as 50 years old should take 200IU vitamin D daily, adults aged 51-65, 400IU daily, and adults older than 65, 600IU daily.

As i've already explained, these levels of intake could be difficult to achieve through diet alone. In Malaysia, there is a insufficient a tablet/oral supplement that has adequate amounts of vitamin D alone; many of the supplements have high amounts of calcium, as well as smaller amounts of vitamin D. If you take these types of supplements to get the recommended levels of vitamin D, you end up with an excessive amount of calcium.

Actually, there are suggestions that the daily recommendation of 600IU is too low, especially in those at risk of vitamin D deficiency, and daily intakes of up to 1,000IU happen to be recommended. From the safety aspect, there's been no proof of toxicity with daily intakes as high as 2,000IU.

Vitamin D, being fat soluble, is kept in body fat. However, although obese people have more fat stores, the vitamin D3 is sequestered deep in their body fat, making it more difficult so that it is released and used. Thus, obese children and adults are only able to improve their blood vitamin D levels by approximately 50% only when compared with normal weighted individuals and therefore are vulnerable to lower vitamin D levels.

In addition, seniors have reduced chance to produce vitamin D from the skin. This, in combination with the truth that many elderly are housebound/in residential care, will make them more likely to be vitamin D deficient. A 70-year-old is only going to have approximately 25% from the capacity to produce vitamin D3 compared with a proper young adult.

Source:health.asiaone.com